1. Field of the Invention
This invention relates to a cooking device and method, and, in particular, to a cooking device and method that is capable of rapidly cooking bread products, such as pizza, muffins, bagels and the like, such that the cooked bread products exhibit a crunchiness. The cooking device is also capable of heating other food products, such as, meats, vegetables and/or garnishes.
2. Description of the Prior Art
In the fast food industry, there is an on going need for faster cooking times for high quality cooking of bread products, such as pizza, muffins, bagels and the like. One type of prior art toaster used in the fast food industry is a contact toaster. An example of a contact toaster is shown in U.S. patent application Ser. No. 09/257,149, filed on Feb. 24, 1999, assigned to the same assignee as this application, now U.S. Pat. No. 5,983,785, granted Nov. 16, 1999. This patent discloses a contact toaster in which a bread product is conveyed by a conveyor belt in pressure contact with a surface of a heated stationary platen. Contact toasters generally toast only one surface of a bread product, such as the surface that is pressured against the heated platen. Such contact toasters require a relatively long time to achieve high quality toasting of a bread product, such as a bagel or muffin. Increasing the speed of the conveyor belt and increasing temperature of the platen may decrease toasting time, but could burn the food product or produce product low in temperature.
An example of a non-contact toaster is the common household toaster that uses two electrical heater elements on either side of a slot that holds the bread product. Non-contact toasters of this type toast the opposed generally flat surfaces of a bread product. Such toasters generally include a rheostat control that allows regulation of the heater element temperature so that the temperature can be increased or decreased depending on the product being toasted. For example, the temperature may be increased to obtain better and faster toasting for a thick bread product, such as a muffin or a bagel. Frequently, the temperature for a desired toasting time is so hot that the bread product burns.
Tunnel ovens that use air impingement heating are known for cooking a broad range of food products, including pizza. An example of a tunnel oven is shown in U.S. Pat. No. 4,873,107. This patent discloses a pair of oppositely rotating conveyor belts arranged to form a gap along a cooking path. Separate heated air manifolds are positioned with each conveyor belt for directed pressurized hot air on the upper and lower surfaces of a pizza item conveyed along the cooking path in the gap. A tunnel oven of this type is capable of cooking a food product at high temperature in a short time without burning. However, there is still a need for tunnel ovens with even faster cooking times. Conventional tunnel ovens do not have any capability to impart crunchiness to the cooked food product.
The tunnel oven of U.S. Pat. No. 4,873,107 uses rectangularly cross-sectioned air jet apertures spaced from one another and from the food items so as to diffuse or plume prior to impingement on the food items. This provides a very even cooking pattern on the food items, thereby tending to prevent streaking on the surfaces thereof. The air jet arrangement allows air flow tuning without disturbing lateral imbalance across the air jet finger by adjustment of fan speed. This tuning, when used with vertical height adjustment of the upper plenum or air jet finger, accommodates food items of varying heights. That is, a manual vertical height adjustment is needed to accommodate food items of different heights.
Thus, there is a need for a tunnel cooking device with even faster cooking times.
There is also a need for a cooking device that can achieve high quality and fast toasting without burning and still provide the crunchiness of a toasted bread product.
There is also a need for a tunnel cooking device with tuning capability to accommodate food items of varying heights without adjustment of the vertical height of the air jet fingers.
The present invention provides a cooking device that meets the aforementioned need for faster toasting/cooking without burning and still providing crunchiness.
The present invention provides a cooking device that heats food products and garnishes.
A cooking device according to one embodiment of the present invention includes a housing having an inlet and an outlet. A toasting/cooking passageway is defined within the housing. A conveyor assembly moves food products inserted at the inlet along the toasting/cooking passageway. A heated air impingement assembly is arranged to deliver to a top surface of the food product hot air for heating the food product as well as for browning the top surface. An electrical heater is located below the passageway for delivering heat and infrared energy to a bottom surface of the food product. After toasting/cooking, the food products are delivered to the outlet.
The hot air has a temperature that rapidly heats the food product to a toasting temperature in less than 60 seconds. The hot air provides a temperature environment that facilitates the infrared heat to produce a crunchiness effect of the bottom and side surfaces of the food product by the end of the rapid toasting time.
The conveyor assembly has a conveyor belt loop that is spaced from the heated air impingement assembly by a gap. The passageway is located in the gap. Preferably, the air impingement assembly is adjustable by raising and lowering to vary its distance above the food product and thus vary the hot air velocity at the point of impingement.
Preferably, the heated air impingement assembly and the electrical heater assembly can be structured to provide two or more toasting/cooking areas along the passageway so that different toasting/cooking temperatures and air velocities can be employed.
In an alternate embodiment, the conveyor belt assembly has a pair of side by side lower belt loops that form side by side passageways with the air impingement assembly. This allows each passageway to be set for concurrent toasting/cooking of food products of different thickness or height. Alternatively, the passageway gaps can be the same so as to double the toasting/cooking capability of same thickness food products.
In another alternate embodiment heated impingement air is also delivered from below the food product. The electrical heating assembly is disposed relative to columns of the heated impingement air so that there is no substantial interference between the infrared energy and the impingement air.
In still another embodiment of the cooking device of the present invention, thermal energy is delivered to a top and a bottom of a food product such that the thermal energy delivered to one of the top and bottom is greater than that delivered to the other. The thermal energy is delivered at least in part by an air impingement assembly that provides upper columns of air to the top and lower columns of air to the bottom.
The delivery mechanism comprises a means for heating the air that forms the upper and lower columns of air and a first heater disposed between the means for heating and the bottom of the food product. Preferably, the first heater is disposed between the air impingement assembly and the bottom. The first heater preferably includes a heater element that is disposed to weave about the lower columns of heated air without being directly within the first columns of air. The air impingement assembly preferably includes a surface with a plurality of apertures through which the lower columns of heated air are delivered, and the heater element does not overlie any of the apertures.
In alternate embodiments, the first heater is disposed inside the air impingement assembly. The first heater element may be disposed to weave about jet apertures that form the lower columns of heated air so as to provide minimal interference therewith. Alternatively, the heater element may be disposed in the lower plenum nearer to a fan assembly.
According to another embodiment of the present invention, the cooking device also comprises an oven cavity and a heating chamber. The air impingement assembly is at least partly disposed in the oven cavity, and the first heater is disposed in the heating chamber. The means for delivering preferably provides a circulating air stream that is heated by the heating means. The circulating air stream is divided into a first path that includes the lower columns of air and into a second path that includes the upper columns of air. The first heater boosts the temperature of the circulating air stream in the first path above the temperature of the circulating air stream in the second path.
Preferably, the first heater is located either between the air impingement assembly and the bottom of the food product, inside the air impingement assembly or between the air impingement assembly and the heating means.
The means for delivering also comprises a fan assembly disposed in the circulating air stream and the first heater is disposed in the fan assembly. The means for delivering also preferably comprises a divider that divides the circulating air stream into the first and second paths. The first heater is disposed relative to the divider to boost the temperature of the circulating air stream in the first path. The first heater is disposed either in the first path or in the divider, in which case the divider includes a heat transfer communication, such as one or more louvers, with the first path. The first heater may be either a gas heater or an electrical heater.
In the various embodiments, the cooking device may alternatively or additionally comprise means for cooling the air that forms the upper columns of air. Thus, delivery means comprises means for altering the temperature of the lower or upper columns of air. According to one aspect of this embodiment, the means for altering either boosts the temperature of the lower columns of air, cools the temperature of the upper columns of air or both.
The method of the present invention cooks a food product by providing a stream of heated air that is applied as columns of heated air to the top of the food product. Also, heat is provided to the bottom of the food product. The thermal energy applied to the top and bottom of the food product is controlled so that the thermal energy applied to the bottom is greater than that applied to the top.
Preferably, infrared energy is also applied to the bottom of the food product. Alternatively, or additionally, a portion of the stream of heated air is cooled for use in forming the upper columns of air. Preferably, the heated air stream is controlled so that the lower columns of air are warmer than the upper columns of air.
A further embodiment of the cooking device of the present invention comprises a means that includes a plurality of jet apertures for providing columns of impingement air. The columns of impingement air form a blanket of impingement air for cooking food products of different heights without adjustment of the distance between the jet apertures and the food products. The cooking device is capable of cooking the food products of different heights in substantially identical cooking times.
Preferably, the jet apertures have a cross-section that is shaped to provide different BTU delivery rates for cooking the food products of different heights. The cross-section preferably has at least one elongated member with one or more enlarged portions located at an end, a center or a combination thereof. The cross section is preferably selected from the group consisting of: dog bone, jack and starburst.
In an alternate embodiment, the columns of impingement air are directed toward the food products from a direction above, below or above and below the food products. The impingement columns preferably include upper columns and lower columns of impingement air that are directed toward the food products from above and below. A conveyor is preferably provided to move the food products through the blanket of impingement air.
In an alternate embodiment, a control means is provided to control the thermal energy applied to a top and a bottom of the food products with a capability of applying a balanced or unbalanced thermal energy thereto. Preferably, a greater thermal energy is applied to either the top or bottom of the food products than to the other.
In another alternate embodiment, one or more radiant heaters are disposed to provide heat to the food products. One of the radiant heaters is disposed above or below a top or a bottom of the food products and the columns of impingement air are directed to the other thereof. Alternatively, first and second ones of the radiant heaters are disposed above or below the top and bottom sides of the food products. Preferably, a control means is provided to selectively control the on/off states thereof by selecting a state from the group consisting of: both on, both off and one on and the other off.
In a further embodiment of the method of the present invention, food products of different heights are cooked by providing columns of impingement air via jet apertures that form a blanket of impingement air. The blanket of impingement air cooks the food products of different heights without adjustment of the distance between the jet apertures and the food products. The method is capable of cooking the food products of different heights in substantially identical cooking times.
Preferably, the jet apertures have a cross-section that is shaped to provide different BTU delivery rates for cooking the food products of different heights. The cross-section preferably has at least one elongated member with one or more enlarged portions located at an end, a center or a combination thereof. The cross section is preferably selected from the group consisting of: dog bone, jack and starburst.
The columns of impingement air are directed toward the food products from a direction above, below or above and below the food products.
In another embodiment of the method, the thermal energy is controllably applied to a top and a bottom of the food products with a capability of applying a balanced or unbalanced thermal energy thereto.